不韋 呂
Realtime sound spectrogram using FFT or linear prediction. Spectrogram is displayed on the display of PC. リアルタイム･スペクトログラム．解析の手法：FFT，線形予測法．スペクトログラムは PC のディスプレー装置に表示される．PC 側のプログラム：F446_Spectrogram.
Dependencies: Array_Matrix mbed SerialTxRxIntr F446_AD_DA UIT_FFT_Real
Diff: MySpectrogram/LinearPrediction.cpp
- Revision:
- 0:a539141b9dec
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MySpectrogram/LinearPrediction.cpp Fri Feb 17 04:55:10 2017 +0000
@@ -0,0 +1,62 @@
+//-----------------------------------------------------
+// Class for linear prediction
+//
+// 2017/02/11, Copyright (c) 2017 MIKAMI, Naoki
+//-----------------------------------------------------
+
+#include "LinearPrediction.hpp"
+
+namespace Mikami
+{
+ LinearPred::LinearPred(int nData, int order)
+ : N_DATA_(nData), order_(order),
+ r_(order+1), k_(order), am_(order) {}
+
+ // Calculate linear-predictive coefficients
+ bool LinearPred::Execute(const float x[], float a[],
+ float &em)
+ {
+ AutoCorr(x);
+ return Durbin(a, em);
+ }
+
+ // Calculate auto-correlation
+ void LinearPred::AutoCorr(const float x[])
+ {
+ for (int j=0; j<=order_; j++)
+ {
+ r_[j] = 0.0;
+ for (int n=0; n<N_DATA_-j; n++)
+ r_[j] = r_[j] + x[n]*x[n+j];
+ }
+ }
+
+ // Levinson-Durbin algorithm
+ bool LinearPred::Durbin(float a[], float &em)
+ {
+ // Initialization
+ em = r_[0];
+
+ // Repeat
+ for (int m=0; m<order_; m++)
+ {
+ float w = r_[m+1];
+ for (int j=0; j<=m-1; j++)
+ w = w - r_[m-j]*a[j];
+
+ k_[m] = w/em;
+ em = em*(1 - k_[m]*k_[m]);
+
+ if (em < 0) break; // Error for negative squared sum of residual
+
+ a[m] = k_[m];
+ for (int j=0; j<=m-1; j++)
+ am_[j] = a[j];
+ for (int j=0; j<=m-1; j++)
+ a[j] = am_[j] - k_[m]*am_[m-j-1];
+ }
+
+ if (em < 0) return false;
+ else return true;
+ }
+}